Library /sys$common/syshlp/ncphelp.hlb LOOP, EXECUTOR, COUNT number  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Specifies the number of blocks to be sent during loopback
 testing over the executor node. The number must be a decimal
 integer in the range of 1 through 65535. If the parameter is
 omitted, only one block is looped.